Winter weather can be a challenge for both cars and drivers. Motorists learn to drive with caution on winter roads. Many of us have learned from our parents about clearing off cars and allowing them to warm up in winter. Now, experts and experienced drivers sometimes have different views on whether or not a car should be warmed up in winter. The practice of allowing the car to warm up may be outdated and even harmful to cars.

A common practice is to start the car, then clean ice and snow from the windscreen, windows, and roof of the car. In some cases, people will even allow the car to continue to idle while shoveling snow from around the car. Drivers often run out in the cold to start the car, then return to the warmth of their homes to finish getting ready to leave. Cars might be left to warm up for fifteen to twenty minutes or even longer.


The practice of warming up a car on cold winter days stems from the times when car engines had carburetors. In the 1980s, manufacturers started replacing carburetors with electronic fuel injection systems. (1) By the late 1980s, most new cars were fuel injected though some manufacturers continued to make carbureted engines into the 1990s.

A carbureted engine requires time to adjust to cold temperatures before being driven. Drivers had to turn on the car and allow it to idle for about five minutes or so before driving the car. People got into the habit of turning on the car and doing other things like clearing snow from the car while the car warmed up. If a car with a carbureted engine was driven before sufficiently warmed up, it would stall. (1)

Fuel injected engines do not require being left to idle in order to warm up. However, many people are still in the habit of doing this. The problem is that not only does this idling to warm up the car cost extra money and cause unnecessary pollution, but it can be actually harmful to a fuel injected engine.


Fuel-injected engines have sensors that feed extra fuel into the engine to compensate for cold temperatures. This is because the engine uses a mixture of vaporized fuel and air, but the fuel is less likely to evaporate and turn into the necessary fuel vapor in cold temperatures. (1) Adding extra fuel is how the system compensates until the engine temperature rises enough for the fuel to vaporize normally.

However, fuel-injected engines do not warm up by idling. Fuel-injected engines need to be driven in order to warm up. Therefore, while allowing the car to idle to warm up, the system is continually pumping extra fuel into the engine without any progress towards actually warming up the engine. Not only does this wastes a lot of fuel, but it can cause serious problems with the engine.

The fuel is a solvent which strips oil away from the parts of the engine that the oil needs to protect. With cold idling, all the excess fuel could be removing oil from pistons and cylinders that need the oil. (1) This can lead to damage to parts of the engine such as piston rings and cylinder liners. (1)


Once the engine reaches 40 degrees, the car returns to normal fuel consumption rates. (1) Since the fuel-injected engine doesn’t warm up by idling, the motorist should begin to slowly drive the vehicle. Driving at typical residential neighborhood speed is a good way to warm up the engine.

Revving up and taking off at top speed is not recommended. The car should be eased into use on a cold day. Five to fifteen minutes of cautious driving is most beneficial to getting the car engine warmed up. (1)

Some drivers balk at the idea of driving without idling the car first. One of the arguments against forgoing the idling is that steering fluid will be too cold to work properly. While the cold winter weather can make the steering fluid a bit sluggish, the best way to get it moving is to use the steering wheel, which won’t happen while idling. (1)


Experts are divided on their opinions of how much time, if any, a fuel-injected car should be left to idle. The belief is that the car’s oil still needs a small amount of time to be able to work properly. Cold weather causes oil to be thicker and move slower than usual.

Henmueller, the president and COO of the Automotive Maintenance and Repair Association, says that cars should be allowed to idle for two to three minutes to give oil some time to warm up and move smoothly. (3) Shanna Simmons, a technical advisor at Pennzoil, a United States oil company, says that while oil is slower in winter weather conditions, the time needed to warm up is only a matter of milliseconds rather than minutes. (3)

Habits can be hard to break and widespread myths seem to hang on despite debunking. Many motorists will continue to warm up their cars in winter for extended periods of time even if their cars have fuel-injected engines. Hopefully, this article has shed some light on the issue of why warming up car engines in winter is no longer necessary.



 1 Orwig, Jessica. "Stop Hurting Your Engine By Idling The Car When It's Cold Out". Business Insider. N. p., 2016. Web. 20 Dec. 2016.

2 Bennett, Jay. "Warming Up Your Car In The Cold Just Harms The Engine". Popular Mechanics. N. p., 2016. Web. 20 Dec. 2016.

3 Galimberti, Kathryn. "Experts Weigh In: Do You Need To Warm Up Your Car In Cold Weather?". N. p., 2016. Web. 16 Dec. 2016.